code: def sdm_LT(f):
      r"""
      Returns the leading term of ``f``.
  
      Only valid if `f \ne 0`.
  
      Examples
      ========
  
      >>> from sympy.polys.distributedmodules import sdm_LT, sdm_from_dict
      >>> from sympy.polys import QQ, lex
      >>> dic = {(1, 2, 3): QQ(1), (4, 0, 0): QQ(2), (4, 0, 1): QQ(3)}
      >>> sdm_LT(sdm_from_dict(dic, lex))
      ((4, 0, 1), 3)
      """
      return f[0]
  
imports: from itertools import permutations
  from sympy.polys.monomials import monomial_mul, monomial_lcm, monomial_div, monomial_deg
  from sympy.polys.polytools import Poly
  from sympy.polys.polyutils import parallel_dict_from_expr
  from sympy.core.singleton import S
  from sympy.core.sympify import sympify
label_desc: Use image node_id 12 for calling a global function with example usage: sdm_LT(f) and returns: f